Pump



J. DOLZA PUMP Filed Jan. 26, 1956 Inventor w d A z z 1 m VIII H [1| 9| fl 5 wflz f 7. w Q W9 A% fir w i Wfi a "a 0 v Attorney United States Patent ()fiice PUMP John Dolza, Fenton, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 26, 1956, Ser. No. 561,519

1 Claim. (Cl. 103-5) The present invention relates to pumps and more particularly to pumps for pumping fuel in a fuel injection system for an internal combustion engine.

In the operation of a so-called spark ignited internal combustion engine, the combustible charge for the cylinders may be formed by injecting the fuel directly into theinduction air. Since this fuel does not have to be injected directly into the combustion chamber during the combustion process as in a compression ignited engine, the fuel may be injected into an atmosphere having a very low pressure. Accordingly, the fuel pressure in the injection system may be comparatively low, thereby providing a cheaper and more trouble-free installation. However, spark ignited engines normally employ fuels such as gasoline that have a high vapor pressure and accordingly, a pronounced tendency to vaporize. This is especially true when the temperature of the fuel is above atmospheric and/or whenever the pressure thereof is below atmospheric. In the previous injection systems, the waste heat from the engine has raised the temperature of the injection system and the fuel therein sufficiently to frequently cause vaporization of the fuel. Also during the intake stroke of the pump, the pressure of the fuel in the intake passage frequently drops enough to cause vaporization of the fuel. These vapors have passed into and through the system thereby causing at least interference with the proper metering of the fuel to the engine and/or a vapor lock that results in a-complete failure of the operation of the engine.

It is now proposed to provide a fuel pump for a fuel injection system which will materially reduce the likelihood of the formation of any fuel vapors in the vfuel contained therein and which will, in addition, effectively remove any vapors and/or air bubbles that are present therein. This is to be accomplished by providing a fuel pump having an intake that includes a separating chamber which receives the fuel to be pumped through the injection system. This separating chamber preferably has sufficient volume to allow a slow non-turbulent flow of fuel therethrough. Thus any vapor or air bubbles in the fuel will be free to rise to the top of the chamber and be bled through an outlet in the top thereof. By pumping a surplus of fuel into the chamber and out through the outlet as the excess of spill fuel flows therefrom and is returned to the storage tank, all of the vapor and air'bubbles will be flushed from the chamber. The outlet from the separating chamber may include a pressure responsive valve so that fuel may be delivered to the chamber under pressure and a positive pressure maintained in the separating chamber at all times. Thus if the pump cells draw their fuel from the bottom of the tank, they will receive fuel free from vapors and under sufiicient pressure to prevent the formation of any fuel vapors in the intake passages even during the intake stroke. The spill fuel from the separating chamber outlet may be conducted into a cooling jacket that is disposed in heat exchanging relation with the pump cells before it is returned to the storage tank. Thus the spill fuel will reduce the formation of vapors in the pump cells by absorbing heat from the pump cells and the fuel therein and carrying it to the storage tank. It should be noted that the check valve in the separating chamber outlet will maintain a positive pressure in the separating chamber and when the spill fuel flows into the cooling jacket, there will be a sudden and substantial reduction in the pressure of the fuel. This sudden reduction in pressure will result in an appreciable quantity of the spill fuel flashing into vapor. Since the formation of these vapors requires the absorption of some energy, the temperature of the spill fuel will be materially lowered. Accordingly, the amount of heat absorbed from the pump cells will be increased thereby reducing the likelihood of vapor lock occurring.

In the one sheet of drawings:

Figure 1 is a cross sectional view of an engineemploying a fuel injection system embodying the present invention.

Figure 2 is a vertical cross sectional view of a fuel metering pump suitable for use in the fuel injection system of Figure l.

Figure 3 is a cross sectional view taken substantially along the plane of line 3-3 in Figure 2.

Referring to the drawings in more detail, the present invention may be adapted for use on an engine 10 of any suitable design. However in the present instance, this engine .10 is of the so-called V type having a cylinder block 12 with a pair of angularly disposed banks of cylinders 14 therein. Each of the cylinders 14 is charged through an inlet passage 16 that extends through the cylinder heads 18 with one end forming an intake valve seat 20 in one wall of the combustion chamber 22 and the other end opening into a plenum chamber 24 containing throttled air. The induction air may pass through a throttle valve, into the lower portion 26 of the chamber 28, through the filter element 30, into the,

upper compartment 24, and into the intake passages 16.

In order to mix the fuel with the induction air, a fuel injection system 32 may be provided for injecting or spraying fuel directly into the air at any suitable location such as the intake passages '16. The present injection system 32 includes a storagetank for the fuel, a transfer pump 36 for drawing fuel from the storage tank, a metering and distributing unit 38 connected to the transfer pump 36 for metering and/or distributing the fuel into the various intakepassages 16. i

The unit 38 may include a metering pump 40 having a housing 42 adapted to be mounted on a web 44 extending transversely of the cylinder block 12 between the two banks of cylinders 14. The housing 42 may include a chamber in the middle thereof with a pair of aligned bearings '48 disposed on the opposite sides of the chamber 46 to rotatably support a vertical driveshaft 50. The lower end of the driveshaft 50 projects into the camshaft gallery 52 and a gear 54 thereon meshes with a similar gear 56 on the camshaft 58. The driveshaft 50 will therefore rotate in some fixed ratio to the engine speed. Any desired number of cylindrical passages 60 may be radially disposed about the driveshaft 50 so as to be disposed in a common plane and to open into said chamber. A plunger 62 may be reciprocably disposed in each of the cylindrical passages 60 so as to form pumping cells 59 having a pumping chamber 61 supplied through inlet passages 63 and exhaust through outlet passages 65. A cam or eccentric 64 may be mounted Patented Mar. 14, 1961 plunger 62. The rim 68 of this plug 66 seats on a shoulder 70 so that a cavity 72 in the middle of the end will form the pumping chamber 61 communicating with an inlet and outlet valve 74 and 76. The rotation of the eccentric will cause reciprocation of the plunger 62 and thereby cause compression and. expansion of the plug, 66 which will cause the volume of the cavity 72 to increase and decrease, thereby producing a pumping action.

The pump intake 78 may include a separating chamber 80 which receives the fuel at the top thereof under pressure from the transfer pump 36. The inlet passages 63 for the pumping cells 59 may communicate with the bottom of the separating chamber 80. The cross sectional area of the chamber 80 is sutficiently large to allow the fuel to flow gently downwardly free of turbulence and with a low enough velocity to allow any vapor or air bubbles to rise to the top of the chamber 80. Thus if the inlet passages 63 draw from the bottom of the chamber 80, the fuel will be substantially free of any vapors and/or air bubbles. An outlet '82 may be disposed in the top of the separating chamber 80 and the transfer pump may deliver a surplus of fuel to the separating chamber. Thus the vapors etc. collecting at the topof the chamber 80 will be carried away with the spill fuel, thereby leaving a source of substantially pure fuel. for the pump cell intake passage 63.

Outlet 82 and pump inlet passage 63 are thus connected in parallel with respect to transfer pump 36 and separating chamber 80.

The outlet 82 from the separating chamber 80 may include a check valve 84 having a valve plate 86 biased toward the valve seat by a coiled spring 88. When in operation the transfer pump 36 delivers a surplus of fuel to the separating chamber 80. The check valve spring 88 is adjusted to allow a positive pressure to build up in the separating chamber 80 but will open and allow the spill fuel to be discharged therefrom. The check valve 84 should be set to open at a lower pressure than the inlet and outlet valves 74 and 76 to prevent the transfer pump 36 overriding the pump cells 59 and forcing unmetered fuel to flow directly through the pump cells 59. By setting the check valve 84 properly, a positive pressure will be maintained in the separating chamber 80 and in the intake passages 63 even during the intake stroke. This positive pressure will reduce the likelihood of the formation of vapors. Also if vapors form in the spill fuel and create a back pressure therein, for instance when the engine is hot but temporarily inoperative, the vapors will be prevented from backing up into the separating chamber 80 and pump.

The spill fuel from the separating chamber 80 may flow from the outlet 82 into a cooling jacket 90 in the pump housing 42. This cooling jacket is in heat exchanging relation with the pump cells 59. Thus the spill fuel will fiow through the cooling jacket 90 and absorb heat from the pump cells 59 and the metered fuel before being returned to the storage tank. Since the outlet from the cooling jacket is connected directly with the storage tank, when the fuel passes through the check valve 84, the pressure thereof will he suddenly reduced. This sudden reduction of pressure will result in an appreciable quantity of the spill fuel flashing into a vapor. This formation of vapors will absorb energy from the remaining liquid spill fuel and materially reduces the temperature thereof. It is therefore apparent that as a result of this sudden pressure reduction, the cooling effect of the spill fuel on the metered fuel will be greatly increased.

It may thus be seen that a pump has been provided which is particularly adapted for pumping readily vaporizing liquids such as gasoline. Although the invention has been described with specific reference to a particular embodiment thereof, it is to be understood that it is not to be so limited since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claim.

I claim:

A fuel pump adapted to receive fuel under pressure from fuel feeding means connected to a source of fuel having a high vapor pressure, comprising a housing having an inlet adapted to receive said fuel from said fuel feeding means, a separating chamber supplied by said fuel inlet, a fuel branch and a spill fuel branch leading from and connected in parallel with said separating chamber, at least one pumping cell in said housing fed from said fuel branch, a check valve disposed in said spill fuel branch and loaded so as to prevent said fuel feeding means from overriding said pumping cell, a cooling jacket disposed about and in heat exchanging relation with said pumping cell, said cooling jacket being connected to said spill fuel branch downstream of said check valve and having an outlet adapted to return said spill fuel to said source, whereby said spill fuel in passing through said check valve into said cooling jacket is subjected to a reduction in pressure which causes said spill fuel to vaporize and thereby cool said pumping cell.

References Cited in the file of this patent UNITED STATES PATENTS 2,357,870 Beeh Sept. 12, 1944 2,378,165 Waeber June 12, 1945 2,661,796 Davis et al. Dec. 8, 1953 2,753,803 Lawrence July 10, 1956 FOREIGN PATENTS 511,287 Great Britain Aug. 11, 1939 

